1. Field of the Invention
The present invention relates to a method for manufacturing a semiconductor device and a semiconductor device. More specifically, the present invention relates to a method for manufacturing a semiconductor device in which a film is deposited on a semiconductor substrate, and a method for manufacturing a semiconductor device comprising exposing at least a part of the semiconductor substrate during a process for manufacturing the semiconductor device.
2. Description of the Related Art
In recent years, for the purpose of satisfying the increased needs for obtaining higher level of the integration for semiconductor devices, a type of semiconductor device which comprises various types of devices including gate insulating films having different thickness (simply referred as “multi-oxide” hereinafter) is developed. A general method for manufacturing a conventional semiconductor device having multi-oxides will be described in reference to FIGS. 8A to 8D and 9A to 9E.
As shown in FIG. 8A, a device isolation region 112 is formed on a silicon substrate 110, and thereafter an oxide film 114 and an oxide film 116 are formed thereon via a thermal oxidization. Consecutively, a resist layer 118 is formed on the oxide film 116, as shown in FIG. 8B.
The resultant substrate having films thereon is then wet-etched by using an etch solution such as buffered hydrofluoric acid (BHF), as shown in FIG. 8C. The operation provides that the oxide film 114 is removed, as shown in FIG. 8D. Then, the resultant substrate having films thereon is processed with a removing agent, as shown in FIG. 9A, and the resist layer 118 is removed, as shown in FIG. 9B. Then, as shown in FIG. 9C, the silicon substrate surface is cleaned with ammonia-hydrogen peroxide mixture (APM) to remove the particulate contaminants, and after that the residual metals and so on are removed by using diluted hydrofluoric acid (DHF).
Subsequently, an oxide film 122 is formed via a thermal oxidization, as shown in FIG. 9D. This processing provides that two gate insulating films 126 and 128 having different thickness are formed as shown in FIG. 9E.
The related conventional technology is disclosed in JP-A-2000-3,965 (pp. 3, FIGS. 57 to 62) and “Ultra Clean ULSI Technology” of OHMI, Tadahiro (written in Japanese), 1995, BAIFUKAN, Tokyo Japan (pp. 156 to 157).
In general, the removing solution or remover for removing organic compounds such as resist layer 118 contains sulfuric acid hydrogen peroxide solution mixture (SPM) including sulfuric acid as a main component, that is heated at a temperature of not lower than 100 degree. C. (see, for example, JP-A-2000-3,965). However, when the SPM containing sulfuric acid and hydrogen peroxide for removing the resist layer 118, an unwanted chemical oxide film 120 is formed on the surface of the silicon substrate 100 as shown in FIG. 9B, causing difficulty in controlling the thickness of the formed gate insulating film to be thinner. Also, when moisture remains on the surface of the silicon substrate 100, stains such as watermark or the like is formed, causing difficulty in controlling the uniformity of the quality of the formed film.
Meanwhile, the recent technical progress in the miniaturization of the semiconductor devices requires improving the switching rate of transistors by designing the transistor to have a shorter gate length. In order to provide shorter gate length for the transistor, the thickness of the gate insulating film should be formed to have thinner film thickness, and therefore a technology for controlling the film thickness of the formed film to be thinner is required.
Further, while the technology for providing the film thickness of the formed film to be thinner is required, the device design of having shorter gate length of the transistor causes a problem, in which the gate leakage electrical current increases to a considerable level. Thus, it is expected to solve the problem by employing a conventionally used insulating film having higher dielectric constant than silicon oxide (SiO2) film (hereinafter referred as “high-k film”) to provide physically thicker film while maintaining the dielectric properties thereof.
However, the high-k film generally involves a problem of having lower thermal resistance, and thus when a high-k film is formed directly on the silicon substrate, a chemical reaction between the high-k film and the surface of the silicon substrate during thermal processing causes the device properties to deteriorate. Therefore, it is proposed to provide a silicon oxide film between the high-k film and the silicon substrate to inhibit such deterioration of the device properties (see, for example, JP-A-2001-274,378). In this case, the thickness of the formed silicon oxide film is preferably controlled to have as thin a film thickness as possible, in order to maintain the driving capacity of the gate.